> For the complete documentation index, see [llms.txt](https://legacy.thehacker.recipes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://legacy.thehacker.recipes/evasion/av/stealth.md).

# Stealth with C2

This technique can be used only after having obtained an initial access on the target

{% hint style="danger" %}
**This is a work-in-progress**. It's indicated with the 🛠️ emoji in the page name or in the category name. Wanna help? Please reach out to me: [@\_nwodtuhs](https://twitter.com/_nwodtuhs)
{% endhint %}

## What is a Command & Control (C2) Reminder

## Cobalt / Havoc

once you have a shell on the victim, one of the most discreet ways to execute code is through object file because the idea is to avoid creating a sub-process but rather to allocate memory to run code and then resume its initial size.

#### Object file

Here is an example of how to launch the BoF (Beacon Object File) once compiled. The source code is available [here ](https://github.com/CMEPW/bof-collection/blob/main/src/checkVM/checkVM2.c)and the goal is to verify if we are dealing with a virtual machine or not.

<figure><img src="https://2817308836-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MHRw3PMJtbDDjbxm5ub%2Fuploads%2FKh5qWNTPJylihULcAYze%2Fbof-VM.png?alt=media&amp;token=72ccecc3-5cd0-4f71-be20-da2c98531162" alt=""><figcaption></figcaption></figure>

#### How to write BoF (Beacon Object File)

For example, if you need the `RegCloseKey` function.

Look at the Windows documentation (in our example <https://learn.microsoft.com/en-us/windows/win32/api/winreg/nf-winreg-regclosekey>) to get the list of the arguments.

In our case :&#x20;

```c
LSTATUS RegCloseKey(
  [in] HKEY hKey
);
```

Then, get the name of the library used (at the bottom of the page) in our case it is : `Advapi32.lib`

We have to structure it like this : `DECLSPEC_IMPORT LSTATUS WINAPI <lib>$<Function>(<Args List>);`

Still in our case, we will get this: `DECLSPEC_IMPORT LSTATUS WINAPI ADVAPI32$RegCloseKey(HKEY);`

Simply use the function like this in our code: `ADVAPI32$RegCloseKeyA(hKey);`

{% hint style="info" %}
*In addition, to use theses functions download the library "beacon.h" available* [*here*](https://hstechdocs.helpsystems.com/manuals/cobaltstrike/current/userguide/content/beacon.h)*.*
{% endhint %}

It is also possible to load a library and then call the method using methods like `GetProcAddress` or `LoadLibraryA.`

Below is an example of how to use this approach:

{% embed url="<https://github.com/CMEPW/bof-collection/blob/main/src/getAV/getAV-ll.c>" %}

More information at this URL: <https://hstechdocs.helpsystems.com/manuals/cobaltstrike/current/userguide/content/topics/beacon-object-files_main.htm>.


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